Heat-sensitive copying material

ABSTRACT

A HEAT-SENSITIVE COPYING MATERIAL COMPRISING A SUPPORT HAVING A HEAT-SENSITIVE LAYER THEREON WHICH COMPRISES A PRIMARY AROMATIC AMINE, AN AZO COUPLING COMPONENT AND A COMPOUND WHICH IS STABLE AT ROOM TEMPERATURE BUT WHICH IS CAPABLE WHEN HEATED OF PROVIDING NITROSONIUM ION IN THE HEATED AREAS OF THE COPYING MATERIAL IN AN AMOUNT SUFFICIENT TO DIAZOTIZE AROMATIC AMINE. THERMAL IMAGING PROCESSES EMPLOYING SUCH MATERIAL ARE ALSO DISCLOSED.

3,694,247 HEAT-SENSITIVE COPYING MATERIAL Robert Charles Desjarlais, South Hadley Falls, Mass, assignor to The Plastic Coating Corporation, South Hadley, Mass. No Drawing. Filed May 11, 1970, Ser. No. 36,440 Int. Cl. B41m /18 US. Cl. 117-36.9 19 Claims ABSTRACT OF THE DISCLOSURE A heat-sensitive copying material comprising a support having a heat-sensitive layer thereon which comprises a primary aromatic amine, an azo coupling component and a compound which is stable at room temperature but which is capable when heated of providing nitrosonium ion in the heated areas of the copying material in an amount sufiicient to diazotize aromatic amine. Thermal imaging processes employing such material are also disclosed.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to a heat-sensitive copying material which, when differentially exposed to heat, results in an azo dye image or trace in those areas of the copying material which were so exposed. The invention also relates to thermal imaging processes wherein such a copying material is employed, and to the products obtained from such thermal imaging processes.

Description of the prior art The art of thermographic recording is a relatively old and extensive art which comprises a large number of processes and materials designed to be employed in reproducing or recording information through the use of heat as the primary energy source to produce the record or image.

It includes processes such as 3M companys Thermofax process, which uses infra-red light to duplicate the infra-red absorbing heat of an original by way of a direct reflex copying process, as well as processes wherein there is physical contact of heat responsive materials with heated instruments, such as platens or styli to produce an original image. This art is to be distinguished, however, from related arts, such as photothermography, wherein the image or latent image is formed, at least in part through the use of light energy, but which may be subsequently developed through the use of heat energy.

Although, as indicated above, there are a relatively large number of processes and materials available for use in thermographically copying or recording of information and data, a number of drawbacks have been associated with many of these processes and products. For example, some of the prior art processes exhibit relatively narrow latitudes with regard to processing parameters; and many of the prior art thermographic materials require supports having particular properties within fairly narrow limits, are available in a limited number of image colors, some or all of which may not be particularly acceptable from an aesthetic point of view, or require that the heat-reactive components of the material be applied in separate layers and kept out of contact with one another United States Patent 0 ice until the material is thermally developed. In some instances one or more of the reactants are carried in an entirely separate sheet, which is brought into contact with the copy sheet just prior to its exposure to heat.

SUMMARY OF THE INVENTION The heat-sensitive copying materials of this invention comprise a support having a heat-sensitive layer thereon comprising (1) a primary aromatic amine which is capable, upon diazotization and coupling, of forming a colored azo dye, (2) an azo coupling component, and (3) a compound which is stable at room temperature, but which is capable, upon heating, of providing nitrosonium ion in an amount sufiicient to diazotize the aromatic amine in the areas of the copying material which are subjected to heat.

Since the resultant image or trace which is obtained in the copying materials is an azo dye image, a wide variety of colors are obtainable with the heat-sensitive copying materials of this invention, depending primarily on the combination of aromatic amine or amines and azo couplers or coupling components which are employed in the heat-sensitive layer. There is no need to apply and/or maintain the various components of the heat-sensitive layer in separate coatings or layers until the copying material is developed or imaged, nor is there any need to incorporate one or more of the components of the heat-sensitive layer in a separate sheet which is brought into contact with the copy material just prior to imaging or development. The heat-sensitive copying materials are stable materials which can be stored at room temperature over extended periods of time with little or no noticeable deterioration, and they are capable of being used in a number of diiferent thermographic copying processes, including those which apply heat to the copying material by means of convection, conduction, radiation, or reflected radiation.

The imaged or developed heat-sensitive copying materials of this invention also have an add-on capability, in that they may be re-imaged or re-developed to add additional information or data in addition to that originally obtained upon initial imaging or development.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As indicated above, the heat-sensitive copying materials of the present invention comprise three essential components: a primary aromatic amine which is capable of being diazotized and coupled to form a colored azo dye; an azo coupling component; and a compound which is stable at room temperature but which is capable, upon heating, of providing nitrosonium ion in an amount sufficient to diazotize the aromatic amine in those areas of the copying material which are subjected to heat. Any of the numerous aromatic amines which have been disclosed as being useful in preparing diazoniurn salts for use in diazotype processes of the prior art can be employed as the amine components in the copying materials of this invention. Similarly, any of the numerous azo coupling components which have been disclosed as being useful in the diazotype processes of the prior art can be employed as the azo coupling components in the copying materials of this invention, and the choice of amine and azo coupling components depends primarily on the color desired in the imaged or developed product.

CH3 dianisidine O C H; -w

Nm) dichloro dianisidine o-chloroaniline; m-chloroaniline; 2,5-dichloroaniline; 3,5- bis(trifiuoromethyl) aniline; 2-chloro-5-trifluoromethyl aniline, o-phenyl sulfonyl aniline 5-chloro-2-phenoxy aniline; 5-chloro-2-(p-chlorophenoxy) aniline, and the like, and para phenylene diamines, including unsubstituted p-phenylene diamines, p-phenylene diamines which are mono substituted in the ortho or meta positions, and para phenylene diamines which are disubstituted in the 2 and 6, 3 and 5, 2 and 3 or 2 and 5 positions, wherein the substituents are selected from the class consisting of halogens, alkyl groups, alkoxy groups, (neutralized) carboxy groups, acetoxy groups, carbamoyl groups, and cyano groups, e.g.

(N,N dimethyl)-p-phenylene diamine; N,N-diethyl-p-phenylene diamine; N,N-diethoxy-p-phenylene diamine; N,N-di(2-hydroxypropyl)-p-phenylene diamine; N-methyl N-allyl-p-phenylene diamine; N,N-dibutyl-p-phenylene diamine; N,N-diamyl-p-phenylene diamine; p morpholinoaniline; p-oxazolidino aniline; N-cyclohexyl p-phenylene diamine; 3-methyl-4-(N,N-dihydroxyethyl) amino aniline; 3-methyl-4-(N-ethyl) amino aniline; 3-methyl-4-(N,N dimethyl) amino aniline; 2-methyl-4- [N-methyl-N-(Z-hydroxy propyl)] amino aniline; 3-ethoxy-4-(N,N dimethyl) amino aniline; 3-methoxy-4-(N-cyclohexyl-N-propyl) amino aniline; 3-chloro-4-(N,N diethyl) amino aniline; 2-ethoxy-4-(N,N-diethyl) amino aniline; sodium-2-carboxy-4(N,N-dimethyl) amino aniline; sodium-2-carboxy-4-(N,N diethyl) amino aniline; 2,5-diethoxy-4-(N-acetoxy) amino aniline; 4-amino-diphenyl amine; 4-amino-3-methoxy-diphenylamine; 4-amino-4'-methoxy-diphenylamine; 4-amino-2,S-diethoxy-benzanilide; 4-amino-2,S-dimethoxy-benzanilide; 3-amino-6-benzoylamino-4-cresol methyl ether;

3-chloro-4-benzoylamino-6-methyl aniline; 4-amino acetanilide; 4-amino-n-methyl-acetanilide and the like.

The preferred aromatic amines are those which are substantially colorless materials which are resistant to oxidation and are non-hygroscopic and which, upon diazotization, form a diazonium compound which exhibits a high rate of coupling and yields, upon coupling, an azo dye having a high extinction coeflicient and good, bright color. Illustrative of such preferred aromatic amines are amines such as dianisidine 0 C H; (I) C H: (Q-Q 4-benzamido-2, S-diethoxyaniline r portion, -Q-r-r l H A OCHzCH: J 4-benzamido-2,5-diethoxyaniline f 0 C H| -Q (5 C H: J 6-benzamido-4-methoxy-m-toluidine f' 0 C H:

I l l CH3 J With regard to the azo coupling component, any of those which have been found to be useful in preparing conventional diazotype materials can be employed to prepare the heat-sensitive copying materials of this invention. However, it has been found that if an azo-coupling component contains acidic groups in the molecule, these groups should be neutralized before such a coupling component is employed in the heat-sensitive-copying materials of this invention, since the presence of such groups can cause premature diazotization of the aromatic amine, which, in turn, results in premature coupling and formation of the azo dye. Illustrative of the azo-coupling components which can be employed in the heat-sensitive copying materials of the present invention are compounds such as resorcinal; 2 methylresorcinol; 4 methylresorcinol; 5 methylresorcinol; 2 methyl 4 ethylresorcinol; 2,4- dichlororesorcinol; 4,6 dichlororesorcinol; 4 chlororesorcinol; 4 bromoresorcinol; 4 iodoresorcinol; 4-fluor0- resorcinol; N(fl hydroxyethyl)rat-resorcylamide; a-resorcylamide; a resorcylic acid; sodium salt; N(phenyl) cc resorcylamide; resorcinol 5 sulfonic acid, sodium salt; resorcinol-4-sulfonic acid, sodium salt; resorcinol-4,6- disulphonic acid, disodium salt; resorcinol, monomethyl ether; resorcinol mono-benzoate; resorcinol mono-acetate; resorcinol mono-formate; fl-resorcylic acid, methyl ester; B-resorcylic acid amide; B-resorcylic acid, sodium salt; anaphthol; fi-naphthol; 2,3 dihydroxynaphthalene; a-resorcylic acid, methyl ester; a-resorcyclic, acid amide; 4- bromo-3,5 dihydroxybenzoic acid, sodium salt; 4-bromo- 3,5 dihydroxybenzoic acid amide; 4 chloro-3,5-dihydroxy benzoic acid amide; bis-(2,4 dihydroxyphenyl sulfide); bis-(2,4 dihydroxyphenyl sulfoxide); the condensation product of S-aminoresorcinol and cyanuric chloride; hydroquinone, monomethyl ether; phloroglucinol; phloroglucinol, mono-methyl ether; 2,4,6 trihydroxytoluene; o hydroxydiphenyl; meta hydroxyphenyl urea; 3,3',5- trihydroxydiphenyl; 2,2',4,4 tetrahydroxydiphenyl; 3,3- 5,5' tetrahydroxydiphenyl; 2,4,6 trihydroxybenzoic acid, sodium salt; 2,3 dihydroxyn aphthalene-6-sulfonic acid, sodium salt; 1 naphthol 2 sulfonic acid, sodium salt; 1 naphthol 3 sulfonic acid, sodium salt; l-naphthol 4 sulfonic acid, sodium salt; 2 hydroxynaphthalene 3,6 disulfonic acid, disodium salt; 1,8-dihydroxynaphthalene 3,6 disulfonic acid, disodium salt; 2,7- dihydroxynaphthalene 3,6 disulfonic acid, disodium salt; 1,8 dihydroxynaphthalene 3,5 disulfonic acid, disodium salt; 8,8 dihydroxynaphthalenelsulfonic acid, sodium salt; 1,8 dihydroxynaphthalene-3- sulfonic acid, sodium salt; 2,8 dihydroxynaphthalene-6- sulfonic acid, sodium salt; 3,8 dihydroXynaphthalene-6- sulfonic acid, sodium salt; 8 acetylamino-1-naphthol-5- sulfonic acid, sodium salt; 2 hydroxynaphthalene 6- sulfonic acid, sodium salt; 2-hydroxynaphthalene-4- sulfonic acid, sodium salt; 2 hydroxynaphthalene 6,8- disulfonic acid, disodium salt; 2 hydroxynaphthalene-7- sulfonic acid, sodium salt; 1 hydroxynaphthalene-Sjdisulfonic acid, disodium salt; 2 hydroxy 3 naphthoic acid anilide; 2 hydroxy 3 naphthoic acid (3' nitro) anilide; 2 hydroxy 3 naphthoic acid (3' trifiuoromethyl) anilide; 2 hydroxy 3 naphthoic acid (4'- chloro) anilide; 2 hydroxy 3 naphthoic acid (4'- methoxy) anilide; 2 hydroxy 3 naphthoic acid (2'- methoxy) anilide; 2 hydroxy 3 naphthoic acid (2- methyl) anilide; 2 hydroxy 3 naphthoic acid (4- methyl) anilide; 2 hydroxy 3 naphthoic acid (3'- methyl) anilide; 2 hydroxy 3 naphthoic acid (2',5- dimethoxy) anilide; 2 hydroxy 3 naphthoic acid-lnaphthylide; 2 hydroxy 3 naphthoic acid 2 naphthylide; 2 hydroxy 3 naphthoic acid (2' methyl, 4'- chloro) anilide; 2 hydroxy 3 naphthoic acid (2- chloro) anilide; 2 hydroxy 6 methoxy 3 naphthoic acid (2' methyl) anilide; acetoacetanilide; benzylacetoacetamide; acetoacetanisidide; acetoacet 0 chloroanilide; acetoacet p chloroanilide; acetocet 2,5 dichloroanilide; acetoacet 2 ,4 dimethoxyanilide; acetoacet 2,5 dimethoxyanilide; acetoacet 2,4 dimethoxychloroanilide; acetoacet a naphthyl amide; acetoacet p anisidide; acetoacetglycinamide; 1 phenyl-3- methyl 5 pyrazalone; l phenyl 5 pyrazalone-3- carboxylic acid amide; l (benzene 2' sulfonic acid)- 3 phenyl 5 pyrazalone, sodium salt; 1 (benzene- 3' sulfonic acid) 3 methyl 5 pyrazalone, sodium salt; 1 (benzene 4' sulfonic acid) 3 methyl-5- pyrazalone, sodium salt; 1 hydroxy 2 naphthoic acid l-hydroxy-Z-naphthoic acid anilide Naphthol AS-D acetate, propionate, furoate, octoate, benzoate, and the like (i.e. a compound represented by the formula QAEOR CN 1| I Q 0 l wherein R represents an acyl radical such as 0 II C... o

o o II II omtonm-oa and the like); Naphthol AS-OL acetate, propionate, furoate, octoate, benzoate, and the like (i.e. a compound represented by the formula (iKlHa wherein R represents an acyl radical such as and the like); Naphthol AS acetate, propionate, furoate, octoate, benzoate and the like (i.e. a compound represented by the formula and the like); 2-hydro xy-3-naphthoic acid morpholide 2-hydroxy-3-naphthoic acid (N-fi-hydroxyethynamide and the like. Illustrative of the types of azo-coupling components containing. acidic groups which can be employed in the heat-sensitive copying materials of this invention if the acidic groups are neutralized prior to the use of such coupling components in said materials, are compounds such as 1 hydroxy 2 naphthoic acid; 2 hydroxy- 3-11aphthoic acid; 2 hydroxy 1 naphthoic acid; 2- hydroxy 6 naphthoic acid; 1 naphthol 4 sulfonic acid; 1,8 dihydroxynaphthalene 4 sulfonic acid; 7- resorcylic acid; a-resorcylic acid; fi-resorcylic acid; 2,4,6- trihydroxybenzoic acid; 4 bromo 3,5 dihydroxybenzoic acid; resorcinol-4-sulfonic acid; and the like.

With regard to the third essential component of the heatsensitive copying materials of this invention, namely the nitrosonium ion source, any compound or combination of compounds which is sufficiently stable at room temperature to avoid prediazotization of the aromatic amine component(s), and yet sufficiently heat-sensitive so that at elevated temperatures nitrosonium ion is liberated in amounts sufiicient to diazotize the aromatic amine, can be employed. The preferred class of nitrosonium ion sources for use in the present invention are substituted and unsubstituted ammonium nitrite salts having the general formula or wherein R 18 hydrogen, a substituted or unsubstituted alkyl group containing from 1 to about 6 carbon atoms, a substituted or unsubstituted aralkyl group containing from 7 to about 10 carbon atoms, or a cycloalkyl group containing from 4 to about 8 carbon atoms, and R" is as inorganic salts of nitrous acid with amine salts of organic or inorganic acids. When the ammonium nitrite salts are formed in situ, the use of alkali metal salts of nitrous acid in combination with amine salts of aromatic organic 5 acids is preferred. Although the aromatic organic acid an alkylene group or heteroalkylene group (i.e. an alkylene portion of the amine salt may be an organic carboxylic, group containing a hetero atom such as oxygen, nitrogen, sulfonic, sulfinic or phosphonic acid, amine salts derived sulfur, and the like in the alkylene chain) containing from from a substituted aromatic carboxylic acid such as sali- 3 to about 7 atoms. Secondary ammonium nitrite salts (i.e. cylic acid are particularly preferred. The amine portion of those wherein two of the groups represented by R are 10 the amine salt is preferably derived from an amine having hydrogen) are preferred. a pKa of from about 5 to about 11.5, with amines having The aforementioned ammonium nitrite salts may be a pKa of from about 8 to about 9 being particularly preadded as a separate and distinct component, or they may ferred. Illustrative of the preferred amines are amines such be formed in situ from ammonium nitrite precursors, such as those set forth in the following table:

TABLE 1 Amino Formula pKa Sec.-buty1 arnirm CH: 10. 56

CHa-CHz-(E-NH N-methyl-N-efhanolaminn CH3 CHnGHzOH 9.88

\ N l H Ethanolamine NHzCH2C- 20H 9.44

Diethanolamlne /CH2CHz0H 8. 9

CHr-CHzOH N-ethyl-N-ethanolamine CHaCH:

CHnCHzOH N-methyl-N-(n-butybamine /OH:

OHZCHHOHZCH:

N-isopropyl-N-ethanolamine CH: 8. 87

/C H HN\ CH3 CHZCHlOH Dl-n-propyl amine CHzCHzCHa 11. 0

CHzCHzCHa n-Butyl amine NHz-CHzCHrCHzCHs 10.6

N(n-butyD-N-ethanolamine /OH;OHCH2OH= CHQCHZOH Di-n-butyl amine CHzCHzCHzCHa 10. 25

CHzCHnCHzCBh Dibenzylamlne 8. 52

2,6 dimethy1mornhn"n .r. H ,r O

emf j-om 1Y1 H Hoxarnethylene imine.. 11.07

When the nitrosonium ion source is an ammonium nitrite salt which is added as a separate and distinct comane, causing the precipitation of the ammonium nitrite salt of whichever amine is employed. The ammonium nitrite ponent, said salt can be prepared beforehand by slowly 70 salt can be recovered by filtration; and, after being washed adding an aqueous solution of alkali metal nitrite (e.g. a 40% solution of sodium nitrite) to concentrated (96%) sulfuric acid. The nitrous acid which evolves from this addition of alkali metal nitrite to concentrated sulfuric with a solvent such as hexane and dried, can be employed as the nitrosonium ion source in the heat-sensitive copying materials of the present invention. Illustrative of the types of ammonium nitrite salts which have been found to be acid i hen directed into a solution of an amine in hex- 75 useful as nitrosonium ion sources in the heat-sensitive copying materials of this invention are ammonium nitrite salts such as N-phenyl (a-hydroxy)ethyl-N-cyclohexylammonium nitrite i, am

Melting point 90-93 C.

diethyl ammonium nitrite 9 ONO Melting point 86-87 C.

Melting point 137-138 0.

dicyclohexyl ammonium nitrite I 6 H2 ONO Melting point 195197 C.

isopropylcyclohexylammonium nitrite 05a 63 CH-N ONO Melting point 150152 C.

u,adimethy1 dibenzyl ammonium nitrite Melting point 168-475" C.

65 N-benzyl-N-isopropyl ammonium nitrite CHa CH-N-CHZ C a H2 9 ONO Melting point 114-1 15 C.

N-(2-cyano) ethyl-N-cyclohexyl ammonium nitrite lib NO Melting point -96 C.

and the like.

If, however, the nitrosonium ion source is formed in situ from ammonium nitrite precursors such as an alkali metal nitrite and an amine salt of an aromatic organic acid, the amine salt of the aromatic organic acid can be prepared beforehand by slowly adding an amine to a concentrated solution of an aromatic organic acid in an appropropn'ate solvent. This reaction is usually exothermic and the amine salt of the acid will separate on cooling. Thus, for example, if an amine salicylate is desired as one of the ammonium nitrite precursors, the appropriate amine is poured slowly into a concentrated solution of salicylic acid in an organic solvent such as acetone, ether, or methylene chloride; and, after cooling to room temperature and scratching the side of the beaker in which the amine salt is being prepared, the amine salt of salicylic acid precipitates out of the solution and is separated by filtration. In some instances the amine salt is so insoluble that it precipitates out while the reaction mixture is still hot. The alkali metal nitrite and the amine salt of the aromatic organic acid can then be incorporated into the heat-sensitive coating as ammonium nitrite precursors, in order to form the required nitrosonium ion source in situ.

Without wishing to be bound to any particular theory as to the exact chemistry involved in the heat-sensitive copying system disclosed and claimed in the present application, it is believed that the nitrosonium ion source which is employed as an essential component in the compositions of this invention decomposes or dissociates under the influence of heat to provide nitrosonium ion in an amount sutficient to diazotize the aromatic amine component which is also present as an essential component in the heat-sensitive copying materials of this invention. Thus, in those areas of the copying material which have been subjected to heat, it is believed that this decomposition or dissociation of the nitrosonium ion source results in the in situ formation of a diazonium of the arcmatic amine, which in turn, couples with the azo coupling component which is present in said heat-sensitive copying materials to form an azo dye image in those areas of the copying material which have been subjected to heat. Although the specific nature of the nitrosonium ion carrier which is derived upon decomposition or dissociation of nitrosonium ion source with heat has proven to be difficult to determine with any degree of certainty, it is believed to be either nitrous acid, nitrous acid anhydride (i.e. dinitrogen trioxide), nitrous acidium ion (H NO or a nitrosyl compound (i.e. a compound, NOX, wherein X represents an electronegative group such as Cl-, -HSO or Using 2,5 diethoxy-aniline to represent the aromatic amine component, resorcinol to represent the azo coupling component and diethylammonium nitrite to represent the nitrosonium ion source, the following reaction sequence has been proposed to illustrate a possible mechanism involved in the development of the heat-sensitive copying materials of this invention: (1) Decomposition or dissociation of the nitrosonium ion source upon application of heat to provide nitrosonium ion in quantities sufiicient to diazotize the aromatic amine in those areas of the heat-sensitive copying material which have been subjected to heat CHaCEg/CHzCHz CHzCHz e 2 N ZHNO: :IzONO CHaC 2 If the nitrosonium ion carrier is assumed to be nitrous acid, the nitrosonium ion for diazotization of the aromatic amine can be obtained by way of the following equilibrium:

It should also be apparent that if the nitrosonium ion carrier is the anhydride of nitrous acid (i.e. dinitrogen trioxide) nitrosonium ion can be obtained by way of a similar equilibrium:

NO+ N02- Similarly, if the nitrosonium ion carrier is assumed to be the nitrous acidium ion (i.e. nitrous acid which has extracted a proton from either the free amine or another molecule of nitrous acid), the nitrosonium ion can be obtained by way of the following equilibrium:

(2) Diazotization of the aromatic amine in those areas of the heat-sensitive copying material in which nitrosonium ion is present (i.e. in those areas of the heatsensitive copying materials which have been subjected to heat) 0 01120113 0 onions /N=O+H+ -NH1 NO+ N I \H OCHzCHa OCHzCHa (Aromatic N-nitroso (2,5-diethoxyaniline) formation) OCHzCHB OCHzCHg /NO" N=N OH so 3 5 H C H: C Ha C H2 0 Ha (Rearrangement to diazotate) (i) C H2 C H3 -NEN+ H20 0 O HzOHs (Conversion to the diazonium) (3) Coupling of the diazonium compound formed from diazotization of the aromatic amine C Hz 0 H3 0 H NEN OH CHzCHa (resorcinol) OH O CHzC s H N=N 11+ (Azo dye) OHBCHtl When the nitrosonium ion source is formed in situ by, for example, the incorporation into the heat-sensitive layer of ammonium nitrite precursors such as an alkali metal nitrite and amine salt of an aromatic organic acid, it is believed that an equilibrium is established, forming the alkali metal salt of the aromatic organic acid and an ammonium nitrite salt. Using diethylarnine salicylate and sodium nitrite as illustrative examples, the proposed equilibrium can be represented by the following equation:

(diethylammonium nitrite) The ammonium nitrite salt formed by way of such an equilibrium is then susceptible to decomposition or dissociation upon heating to provide nitrosonium ion to diazotize the aromatic amine, which in turn couples with the azo coupling component, in a manner similar to that proposed in the mechanism set forth above. In this instance, however, due to the presence of the acid salt, the nitrosonium ion carrier may in fact be a nitrosyl compound such as nitrosyl salicylate (i.e. a compound having the formula NOX wherein X represents the salicylate ion). Thus, for example, the diethylammonium nitrite in the equilibrium set forth above may react, upon heating, with the sodium salicylate to form nitrosyl salicylate, which provides nitrosonium ion by Way of the following equilibrium:

CHaCHz CHzCHg N e IkzONO ll C-ONO 0 L-0 NO+ At this point it will be apparent to one of ordinary skill in the art that the judicious selection of the acid portion of the amine salt used as an ammonium nitrite precursor can result, upon either the formation of the nitrosonium ion source or the diazotization of the amine, in the simultaneous formation of a species which can serve as the azo coupling component in the heat-sensitive copying materials of this invention. It is intended that this particular embodiment also be included within the scope of the invention disclosed and claimed.

In addition to the three essential components of the heat-sensitive copying materials of this invention which have been discussed in detail supra, these heat-sensitive copying materials can have incorporated therein additional components such as pre-coupling inhibitors, antioxidants, UV (ultraviolet) absorbers, stabilizers, and other types of additives. For example, if a particular nitrosonium ion source or combination of a particular aromatic amine and nitrosonium ion source tends to pre- 21 maturely release nitrosonium ion (e.g. through the premature formation of nitrous acid,

O2':NO+ +N02 which, in turn, would cause premature diazotization and coupling of the amine, small amounts of a precoupling inhibitor such as sodium azide (NaN can be incorporated into the heat-sensitive formulation to deactivate any nitrosonium ion and/ or diazonium which might be formed prematurely. In the case of nitrous acid, a proposed mechanism for such deactivation is:

('1 3N33HN3 +NaNO and In the case of premature formation of the diazonium, a mechanism has been proposed whereby the sodium azide reacts with the diazonium to form a colorless aryl azide which is incapable of coupling with the azo coupling component present in the formulation Other pre-coupling inhibitors such as hydroquinones, including substituted hydroquinones, and arylsulfinic acids can also be employed to deactivate any diazonium which might be formed prematurely (e.g. with hydroquinone, a possible mechanism can be represented by the following formulae:

1. NEN+ HO-Q-OH and With a sulfinic acid, a possible mechanism can be represented by the following formula:

(diazosulfone) As indicated above, the heat-sensitive copying materials of this invention can also contain antioxidants and UV absorbers, in order to prevent oxidation and/ or discoloration of said materials due to oxygen, heat, light, heavy metal ions or any combination of such oxidation initiators. For example, the presence of small amounts of hydroquinone and substituted hydroquinones such as tertiary butyl hydroquinone and chlorohydroquinone have been found to be particularly useful in inhibiting the oxidation and/or discoloration of the aromatic amine component; and the use of UV absorbers which absorb strongly near the visible region of the spectrum has been found to both inhibit the oxidation of one or more of the essential components, and to reduce or eliminate any photoproduction of azo dye. Illustrative of such UV absorbers are materials such as Tinuvin P (a substituted hydroxyphcnylbenzotriazole) Tinuvin 326, Tinuvin 327 and Tinuvin 328 (UV absorbers sold by Geigy Chemical Corporation of Ardsley, N.Y.), as well as other UV absorbers such as 2,2-dihydroxy 4 methoxy benzophenone. The UV absorber can be incorporated into the heat-sensitive layer as an additional component or added to the support which is employed, or it may be applied in a separate layer or over-coat.

Other additives such as buffers or pH adjusters can also be included in the heat-sensitive copying materials of this invention, in order to adjust or maintain the pH of the heat-sensitive layer, thereby improving the stability of the heat-sensitive copying material during storage (Le. improving its shelf-like). Non-hygroscopic, low odor, colorless aliphatic and heterocyclic amines having low vapor pressures have been found to be particularly useful in this regard, with the use of heterocyclic amines such as imidazole being preferred.

Any of the well-known, conventional substrates 0r bases which have been traditionally employed as substrates for diazo-type formulations can be employed as supports in the heat-sensitive copying materials of this invention, the only major requirement being that the support be thermally stable at the temperatures used to image the heatsensitive copying materials comprising such support. Supports which are susceptible to hydrolysis or which tend to release acid over extended periods of time should also be avoided. Illustrative of the types of supports which can be employed to prepare the heat-sensitive copying materials of this invention are supports such as cellulose diacetate, cellulose triacetate, ethyl cellulose, polyester, and the like. The bonding of the heat-sensitive layer to the support can be improved in many instances by either coating the particular support with a subbing layer of a bonding resin, or by incorporating such a resin into the heatsensitive formulation as an additional component. Illustrative of such bonding resins are resins such as polyvinyl butyral, cellulose diacetate, ethyl cellulose, polyvinyl formal, cellulose acetate butyrate, and the like. Polyester film having a bonding or subbing layer of cellulose acetate butyrate coated thereon has been found to be particularly useful as a support for the heat-sensitive copying materials of this invention.

The heat-sensitive copying materials are prepared by coating a solution of the various components onto the proper support using any of the conventional coating techniques, and then drying the coated support at a temperature less than that at which imaging occurs. The temperature at which imaging occurs is not narrowly critical and depends to at least some degree on the particular components employed in preparing the heat-sensitive copying materials of this invention. When employed in a contact or a direct reflex copying process wherein an infrared-absorbing original image is in close proximity to the heat-sensitive copying material, the temperature range available in commercial thermocopying machines such as 3M Companys Thermofax machines (e.g. 3M Companys Sec cretary-Model 45CG) has been found to be more than adequate for development of the heat-sensitive copying materials of this invention.

Depending primarily on the various particular components employed in preparing a given heat-sensitive copying material in accordance with this invention, on the nature of the original being copied, and on the particular copying process being employed, the heat-sensitive copying material may exhibit a tendency to stick to the original being copied. In such instances the heat-sensitive material can be top-coated with a protective layer or coating which is inert with respect to the components employed to prepare the heat-sensitive layer, thereby reducing or eliminating entirely the tendency of the heat-sensitive copying material to stick to the surface of the original. For example,

the use of a polyphcnylene oxide (PPO') coating over the heat-sensitive layer has been found found to be particularly useful in reducing or eliminating this tendency to stick.

As indicated earlier, the sensitive copying materials of this invention can be employed to make copies such as oflice copies, copies for overhead projectuals, and copies of engineering drawings from originals containing infrared-absorbing images, such as carbon, pigmented ink, and silver images; and such materials can also be employed as chart papers, and the like, which are imaged through the use of devices such as heated styli.

The following examples are intended to further illustrate the invention disclosed and claimed herein, but they are not intended to limit the scope thereof in any way. The first time that a particular component is mentioned in any of the following examples, an attempt will be made to describe its intended function in parentheses immediately following the enumeration of the component itself. When the same component is mentioned thereafter in any following examples, a recitation of its intended function will be omitted unless the intended function is different from that given upon first enumeration of such component. Where it is thought that the structural formula of any given component might be of some assistance, such formula will also be provided upon first enumeration of the component in question. All parts and percentages are parts and percentages by weight, and not by volume, unless specifically stated otherwise in the particular example.

Example-A heat-sensitive coating formulation was prepared comprising the following components:

Component Amount Acetone (solvent) ml 60 Methanol (solvent) ml 40 Sodium azide (pre-coupling inhibitor gm 0.07 2-hydroxy-3-naphthoic acid, o-anisidide 1 (azo coupling component) gm 0.71 Dianisidine 2 (aromatic amine) gm 1.32 Di-(acetoacet)-dianisidide 3 (azo coupling component) am 0.83 Sodium nitrite (precursor of the nitrosonium ion source) gm-.. 1.0 Tinuvin P (a substituted hydroxyphenyl benzotriazole UV absorber) gm.. 2.0 N-isopropyl-N-benzylamine salicylate .(precursor of the nitrosonium ion source) gm 4.53 Hydroquinone (antioxidant and pre-coupling inhibitor) ..gm 0.02 l @3011 01130 H=0 OCH;

I CHaO OCH:

l? i if if CHa-C-CHz-C-III- I]\ICCH2-CCH;

The formulation was head coated at a rate of approximately feet per minute onto a polyester film support which had been previously coated with a cellulose acetate butyrate bond coat, and the coated support was then dried for four minutes at 130 F. The resulting heat-sensitive copying material was subsequently top-coated with a 4% solution of polyphcnylene oxide in trichloroethylene and this additional coating was then dried. A sample of the resulting heat-sensitive copying material was imaged by placing the sensitized side of said copying material in intimate contact with a portion of a page from a newspaper and then passing the copying material and the newsprint original while in intimate contact with one another, through a Thermofax Secretary (Model 45CG) thermo- 24 copy machine at a rate of approximately 6 /2 feet per minute. A neutral black copy of the newsprint original which was capable of being used as an overhead projection transparency was obtained.

Examples 2-8.A heat-sensitive coating formulation was prepared comprising the following components:

The formulation was head coated onto a polyester film support which had been previously coated with a cellulose acetate butyrate bond coat, and the coated support was then dried for four minutes at 115 F. The resulting heat-sensitive copying material was then top-coated with a coating formulation comprising the following components:

Trichloroethylene cc Tinuvin 327" (a UV Absorber sold by Geigy Chemical Corporation of Ardsley, N.Y.) gm 3 40% Solution of Acryloid B-72 (a film forming acrylic resin manufactured by the Rohm and Haas Corporation of Philadelphia, Pa.) in toluene gm Polyphenylene oxide, a film forming resin polymer consisting essentially of the repeating polymer unit 1 g 3 l l CHS In The top-coated, heat-sensitive copying material was dried for four minutes at 115 F., and a sample of the resulting material was exposed while in contact with a master containing an infrared-absorbing image and in a manner similar to that set forth in the preceding example to yield a black copy of the image on the master on a clear background.

Additional formulations similar to that set forth above were prepared using azo coupling component(s), an aromatic amine and/ or an amine salt of an aromatic organic acid which were different from those employed in the formulation set forth above. These formulations were coated on the same type of substrate, were dried, topcoated and again dried in the same manner, and then imaged in the same manner as the heat-sensitive copying material obtained from the formulation set forth immediatelly above. The alternative components used and the results obtained are set forth in the following table. Where the component was unchanged from that employed in the formulation set forth above, this is so indicated by the word Same" in the table.

When the solvent balance in the formulations set forth above as Examples 2 to 8 is modified to 80 cc. of acetone and 20 cc. of methanol (rather than 60 cc. of acetone and 40 cc. of methanol) and a suflicient amount of a suitable resin such as 6 to 10 grams of cellulose acetate butyrate is added to increase the viscosity of the formulation, these formulations can then be coated onto thin sheets of paper such as S. D. Warrens 9 pound Dundee White and imaged to provide black copies on a 10 white background.

TABLE II Color Organic acid amine sa1t(s) employed as obtained Ex. precursor(s) of the nitrosonium ion upon No. Aromatic amine Azo-coupling component source(s) imaging 3. Benzoic acid, 2-methyl-4-amino-5- 2,3,dihydroxy-naphthalene Same Red.

methoxy anilide (Fast Violet B Base) 0 CH; OH i Q @C-N- NHQ OH 4 Same 2-11ydroxy-6-methoxy-3-naphthoic Same Green.

acid, o-toluidide 0 CH3 omo oar-Q ll ll 0.195 gm. and acetoacetie acid, benzylamide 0 0 II I CHa-C-CHZ- 11-011 5 Same 2hydroxy-3-naphthoie acid, m s Blue.-

0-anisidide 0 W /OH CHa 6.-.- Benzoic acid, 2-methy1-4-amino-5'- Di(acetoacet) dianisidide-0.83 gm flame Yellow.

methoxyanilide-MS gm.

7.... Same 2,3-dihydroxynaphthalene m Violet.

g Same The azo coupling component was Dibenzylamine a-hydroxy-B-naphthoate Orange.

derived from the dibenzylarnine napthoate which was employed as the precursor of the nitrosonium ion source.

Example 9.A coating formulation was prepared comprising the following components:

28 Component: Amount N phenyl (a hydroxy)ethyl N cylclohexylamine (Precursor of the nitrosonium ion Componentf Amount 0 3 60 T. 2 1; z; Methanol cc 40 5 e ormua 1011 was en coa e on e same ype o v substrate as that employed m Examples 2 to 8, dr1ed, Sodium azide gm 0.07

thi 0 02 top-coated, and agaln dried in the same manner as that Pheno azme T employed with Examples 2 to 8, and then imaged in the chlorohydroqmfloqq f same manner as the heat-sensitive copying materials ob- Di-(acetoacet)d1ams1dide gm- 0.83 10 tained in Examples 2 to 8 to yield a black image on a Dianisidine am 1.32 clear background. 2-Hydroxy-3-naphthoic acid, o-anisidide gm 0.71 Examples 10-12 N p py N benzylammonium nitrite Three coating formulations were prepared comprising (Nitrosonium ion source) gm.. 2.9 the following components:

Amounts Component Example 10 Example 11 Example 12 Acetone. 70 cc 70 cc 70 cc. Methanol- 30 co 30 co 30 cc.

Sodium azide Sodium nitrite Sodium salt of p-toluene sulfinic acid Im i rl am] a Dianisidine. Chlorohydroquinone..--

0.02 gram- 0.02 gram- 0.02 gm. 1.0 gram 1.0 gram 1.0 gm.

0.25 gram. 0.25 gram-.- 0.25 gm. 0.40 gram..- 0.40 gram... 0.40 gm. 0.80 gram-.. 0.60 gram-.- 0.89 gm.

Phenothiazine 0.001 gram.-- 0.001 gram. 0.001 gm.

0.02 gram--- 0 02 gm. 2-hydroxy- -naphthoic acid, o-anisidide 0.92 gram 2-hydroxy-3-naphthoic acid, 3'-(trifluoromethyl) anilide OH CF: W6 0 it (Azo coupling component) 0.28 Br m 1-hydroxy-2-naphthoio acid, morpholide" Azo coupling component) Di-(acetoacet)-dianisidide Z-hydroxy- -naphthoic acid, N-(fi-hydroxyethyl) amide (Azo coupling component) N -isopropy1-N-b enzylamine salicylate 5 .39 grams 5.39 gm,

N-phenyl (a-hydroxy)ethyl-N-cyclohexylamine salicylate (P ecursor 0f the nitrosonium ion source) CHa-CH-Q c 5 4.22 grams (Precursor of the nitrosonium ion source)- k5 second butyrate (a low viscosity cellulose acetate butyrate resin used to increase the viscosity of the formulation).

1.43 grams 10 grams 10 gm.

10 grams *The preparation of such N-substituted-a-l1ydroxy-B-naphthamides are disclosed in copending application Serial No. 667,369, filed on September 13, 1967, the disclosure of which is incorporated herein by way of reference thereto.

Each of the formulations were coated separately onto 100% rag paper of approximately 2.5 mil thickness by means of a No. 24 wire-wound coating rod. The coatings were then dried minutes at 130 F. A sample of each of the resulting heat-sensitive copying materials was processed through a Thermofax Secretary-Model 45 CG thermocopy machine at a rate of approximately six feet per minute with the heat-sensitive copying material in contact with a typewritten original, but with the sensitized side of said copy material away from the carbon ink image of said original. A legible, right-reading facsimile of the original was obtained in each instance. In the case of the heat-sensitive copying material prepared from the formulation identified supra as Example 10, a black image on a white background was obtained. In the case of the material prepared from the formulation identified as Example 11, a blue image was obtained, and in the case of the material prepared from the formulation identified as Example 12, a sepia image was obtained.

Examples 1317.--Five coating formulations were prepared comprising the following components:

60 formulations wherein only the nitrosonium ion source was varied were prepared and coated onto a polyester film support which had been previously coated with a cellulose acetate butyrate bond coat. The formulations were coated at a rate of 15 feet per minute and then dried for six minutes at 130 F. A sample of each of the heat-sensitive copying materials was imaged by passing the sample, while in intimate contact with a carbon-based ink master having a reflected density of 1.45, through a 3M Secretary-Model CG thermocopy machine which was set at a machine speed of approximately 6 feet per minute. In each instance a bright red image was obtained, and densities of both the image areas and the background areas were measured on each sample, using a MacBeth Quanta Log Ditfuse Reflection DensitometerModel RD-100 with a Visual Filter (#106). The density readings which were obtained (Dmax. and Dmin.) are set forth in the table below.

Amounts Component Example 13 Example 14 Example 15 Example 16 Example 17 Acetone"... cc 60 cc 60 cc 60 cc 60 cc. Methanol.-. 40 cc 40 cc 40 cc 40 cc. Sodium az 0.02 gram 0.02 gram...- 0.02 gram.. 0.02 gram. 0.02 gram. Sodium nitrite 1.0 r m 1.0 gram 1.0 r m 1.0 r m 1.0 gram.

Sodium salt of p-toluene sulfinic acid.. Imidazole Dianisidine Chlorohydroquinon Phenothiazine- 2-hydroxy-3-naphth a Di-(acetoacet)-dianisidide 0.25 gram-..- 0.25 gram. 0.25 gram. 0.25 gram 0.25 gram. 0.40 gram 0.40 gram. 0.40 gram 0.40 gram 0.40 gram.

0.80 gram 0.42 gram 0.80 gram. 0.80 gram 0.001 gram 2-hydroxy-3-naphthoic acid, 3"(trifluoromethyl) anilide: 0.28 gram 2-hy droxy-S-naphthoie acid, N-(B-hydroxyethyl) amide. 2, 6-dimeth0xy-4-benzamidoanoline Acetoacetglyclnamide (Aromatic amine) II II II ((OE-C-C H;-CCH,CNH,)) (Azo coupling component) 2-hydroxy-3-naphthoie acid, morpholide Benzoic acid 2'-methy1-4'-amino-5'-methoxy nfliris N-isopropyl- -benzy1amine saiicyl (Azo coupling component) 0,71 2mm 0.40 gram- 2.09 grams--- 2.09 grams.

5.39 grams N- henyl (a-hydroxy) ethyl-N-cyclohexylamine saiicy1ate N- 2-ch1orobenzyl)-N-cyclohexylamine salicylate 4.22 grams. 5.63 grams 1.43 grams 43 grams N-benzyl-N-cyclohexylamiue salicyiate (Precursor oi the nl nnhmflnn source) Color Obtained upon imaging.

Each of the above formulations were separately coated onto the same type of substrate as that employed in Examples 2 to 8 rat the rate of 15 feet per minute, and then dried for five minutes at 130 F. A sample of each of the heat-sensitive copying materials was then processed through a Termofax Secretary-Model 450G thermocopy machine at a rate of approximately 6 feet per minute with the sensitized side of said sample in direct contact with an infrared-absorbing graphic origi-nal. The copy obtained in each instance was suitable for use as an overhead projection transparency.

Examples 1876.--In order to illustrate the wide variety of nitrosonium ion sources which can be employed in the heat-sensitive copying materials of this invention,

3.87 grams. 3.87 grams.

Black Blue Green Violet Red.

The formulation which was used to prepare the heatsensitive copying materials in these examples comprised the following components:

Component: Amount Methanol ml 40 Acetone ml 60 Sodium nitrite "gm-. 1.0 Sodium azide gm 0.02

TABLE III Melting point in Amount, pKa 01 C. of the Example Precursor grams the amine salicylate Dmnx- Data.

18 N-isopropyl-Neyclohexyl amine salieylate 4. 41 166-168 0. 88 0. 04 Morpholine salicy 3. 56 109-111 0. 70 0. 04 Plperidine salicylate 3. 52 119-122 0. 0. 04 D thylamine salicy 3. 33 98-100 0. 0. 04 N-ethyl-N-ethanolamine sali'eylate 3. 59 76-77 0. 0. 04 2, 6-d1methyl morpholine salicylate 4. 00 146-148 0. 0. 04 N -methyl-Nn-butylamine salleyla 3. 56 73-74 0. 47 0. 04 Dibenzyi amine saliey 5. 29 159-161 0. 79 0. 04 N-methyl plperazine salicylate 3. 76 114-119 0. 47 0. 04 Piperazine (mono) salieylate- 3. 54 9. 72, 5. 60 228-232 0. 54 0. 04 tert.-Butyl amine salicylate 3. 34 0. 68 199-205 0. 84 0. 04 Piperazine (di) sallcy 5. 72 9. 72, 5. 60 225-231 0. 60 0. 09 Cyelohexylamine salicylate 3. 74 10. 6 106-108 0. 64 0. 04 31 Di-n-propyl amine salicylato 3. 78 11.0 84-95 0. 58 0.04 32 N-(2 cyanoethyl)-N-cyclohexylamine salicylate 4. 58 8. 2 99-101 0. 96 0. 04 33 Benzylamine salicylate 3. 88 9. 3 92 96 0. 44 0. 04 34.. N-ethyl-N-benzylamine salicylate 4, 32 9. 64 125-127 0. 68 0. 04 35.-- N, N'-diebenzyl ethylene cliamine salieylate 5. 97 120-122 0. 60 0. 10 N-methyl morpholine salicylate 3. 78 7. 38 55-59 1. 06 0. 22 Benzotriazole salicylate 4. 06 8. 20 125-128 1. 10 0. 42 Dieyclohexylamine salicylate 5. 03 ll. 25 191-199 0. 0. 04 3-2 azabieye1o-3.2.2. nonane salicylate 4. 28 10. 48 122-125 0. 32 0. 04 N -isopropyl-N -benzyl amine salicylate 4. 53 148-150 0. 94 0. 04 41. 3,3-imino-di-proplonitrile sallcylate-.. 4. 13 5. 26 70-75 0. 0. 06 42. Di-sec. butylamine salicylate 4, 22 10.91 135-138 0. 60 0. 04 43--- a a dimethyl dibenzylamine salieylate. 5. 74 148-154 1. 14 0. 06 44 Piexamethylene-imine salicylate 3.74 11. 07 -103 0. 20 0. 04 45 N-tert.-butylN-benzylamine salicylate.. 4. 75 238-239 0. 94 0. 04 46 Dieyclopentyl amine salicylate 4. 57 10. 93 147-148 0. 57 0. 04 47-.- N -tert. butyl-N-ethanolamine salicylate 4. 03 -123 0. 75 0. 04 48... N-Phenyl (a-hydroxy) ethyl-N-cyclohexyl amine sa11cylate. 5. 63 9 2 -138 0. 72 0. 04 49..- N-benzyl-N-cyclohexyl amine selicylate 5. 17 -176 0. 78 0. 04 50 N-isopropyl-N-(Z chloro)benzy1 amine salicylate 5. 09 131-132 0. 85 0. 04 51 N-cyclohexyl-N-(Z chloro)benzyl amine sahcylate 5. 72 152-154 0. 85 0. 04 52 N -isopropyl-N-(2,4-diehloro)benzyl amine salieylate 5, 63 154-147 0. 93 0. 04 53 N -cyclohexyl-N-(2,4-dichloro)benzyl amine salleylate 6. 26 135-138 0. 92 0. 04 54. N-Sec. butyl-N-benzyl amine salicylate 4. 79 132-134 0. 82 0. 04 N -sec. butyl-N-(Z chloro)benzyl amine salicylate 5. 31 84-85 0. 95 0. 04 N-sec. butyi-N-(4 ch1oro)benzyl amine salicy1ate-. 5. 31 122-123 0. 87 0. 04 N-cyclohexy1-N-(4 ehloro)benzyl amine salicylate- 5. 72 167-168 0. 79 0. 04 58 N -tert. butyl-N-benzyl amine sallcylate 4. 76 234-235 0. 95 0. 04 59 N -tert. butyl-N-(2 chloro)benzyl amine salieylate- 5. 32 207-208 0. 98 0. 04 60 N-tert. buty1-N-(4 chloro)benzyl amine sallcylate 5. 32 127-129 0. 94 0. 4 61 N-tert. butyl-N-(2,4 dichloro) benzyl amine salieylate--- 5. 85 212-214 1. 12 0. 05 62............ Imidazole salieylate 3. 26 122-125 1. 3 a 10 63 Di-isopropylamine saiicylate 3. 78 117-119 0. 92 0- 4 64. L-2-benzylamino-l-propanol salicylate 5. 01 72-74 1. 00 0. 04 65. N -eyclohexyl-N -ehtanolamine selicylate 4. 43 65-69 0. 74 0. 04 66. N -is0propyl-N-benzylamine salt of benzene phosphorus acid- 4. 59 78-80 0. 64 0. 04 67. N -isopropyl-N -benzylamlne benzene phosphinate 4. 58 2-33 0. 58 0. 04 68. N -isopropy1-N -benzylamine benzene phosphonate. 4. 58 -194 0. 50 0. 04 69- N -isopropy1-N -benzyiamine-o-bromobenzoate-- 5, 53 104-106 0. 57 0. 04 70. N -isopropyl-N -b enzylamine benzoate. 4. 28 101-102 0. 54 0. 04 71. N-isopropyl-N-benzylamine nitrite 3. 10 188-189 0.77 0. 04 72. N-is0propyl-N-benzylamine chloride. 2. 93 188-189 0. 35 0. 04 73. N-isopropyI-N-benzylamine p-toluene sulfonat 5. 07 124-125 0. 44 0. 04 74. N -isopropyI-N -benzylamine phthalate 4. 98 101-102 0. 52 0. 04 75.-. N-isopropyl-N-benzylamine sulfinate- 4. 83 129-131 0. 46 0.04 76 N-isopropyl-N-benzylamine-E-chlorosal 5. 07 120-121 0. 82 0. 04

' In this particular example, the 1.0 gram of sodium nitrite was omitted from the formulation and replaced with 2.53 gm. (15.8

millimoles) of sodium salieylate.

What is claimed is:

1. A heat-sensitive copying material comprising a support having a heat-sensitive layer thereon which comproses:

(A) an aromatic amine which is capable, upon diazotization and coupling, of forming a colored azo dye;

(B) an azo coupling component; and

(C) a nitrosonium ion source which is stable at room temperature, but which is capable upon heating of providing nitrosonium ion in an amount sufi'lcient to diazotize the aromatic amine in those areas of the copying material subjected to heat, said nitrosonium ion source being selected from the class of ammonium nitrite salts having the general formulae:

2. A heat-sensitive copying material as claimed in claim 1 wherein two of the groups represented by R in the ammonium nitrite salt are hydrogen.

3. A. heat-sensitive copying material as claimed in claim 2 wherein the ammonium nitrite salt is at least one salt selected from the class consisting of N-isopropyl-N- benzylammonium nitrite; N-(Z-cyanoethyl)-N-cyclohexylammonium nitrite; dibenzylammonium nitrite; N-phenyl (u-hydroxy)ethyl N cyclohexylammonium nitrite; N- (2 chlorobenzyl) N cyclohexylammonium nitrite; and N-benzyl-N-cyclohexylammonium nitrite.

4. A heat-sensitive copying material as claimed in claim 1 wherein the ammonium nitrite salt is formed in situ from an inorganic salt of nitrous acid and an amine salt of organic or inorganic acid.

5. A heat-sensitive copying material as claimed in claim 4 wherein the ammonium nitrite salt is formed in situ from an alkali metal salt of nitrous acid and an amine salt of an aromatic organic acid.

6. A heat-sensitive copying material as claimed in claim 5 wherein the amine salt employed to form the ammonium nitrite salt in situ is derived from a substituted aromatic carboxylic acid and an amine having a pKa of from about 5 to about 11.5.

7. A heat-sensitive copying material is claimed in claim 6 wherein the amine salt employed to form the ammonium nitrite salt in situ is derived from salicylic acid and an amine having a pKa of from about 8 to about 9.

8. A heat-sensitive copying material as claimed in claim 7 wherein the ammonium nitrite salt is formed in situ from sodium nitrite and at least one amine salt of salicylic acid selected from the class consisting of N-isopropyl-N-benzylamine salicylate; N (2 cyanoethyl)-N- cyclohexylamine salicylate; dibenzylamine salicylate; N- phenyl (a hydroxy)ethyl-N-cyclohexylamine salicylate; N (2 chlorobenzyl) N cyclohexylamine salicylate and N-benzyl-N-cyclohexylamine salicylate.

9. A heat-sensitive copying material as claimed in claim 5 wherein the azo coupling component is derived from the acid portion of the aromatic organic acid employed to form the ammonium nitrite salt in situ.

10. A heat-sensitive copying material as claimed in claim 1 which comprises, as an additional component, at least one pre-coupling inhibitor.

11. A heat-sensitive copying material as claimed in claim which comprises as a pre-coupling inhibitor at least one compound selected from the class consisting of sodium azide, hydroquinone, a substituted hydroquinone and an arylsulfinic acid.

12. A heat-sensitive copying material as claimed in claim 1 which comprises, as an additional component, an antioxidant.

13. A heat-sensitive copying material as claimed in claim 12 which comprises as an antioxidant at least one compound selected from the class consisting of hydroquinone, a substituted hydroquinone, and phenothiazine.

14. A heat-sensitive copying material as claimed in claim 1 which comprises, as an additional component, an ultraviolet absorbing material.

15. A heat-sensitive copying material as claimed in claim 14 which comprises as an ultraviolet absorbing ma- 34 terial at least one compound selected from the class consisting of a substituted hydroxyphenylbenzotriazole and 2,2'-dihydroxy-4-methoxy benzophenone.

16. A heat-sensitive copying material as claimed in claim 1 which comprises, as an additional component, a non-hygroscopic, low odor, colorless, low vapor-pressure aliphatic or heterocyclic amine as a pH adjuster.

17. A heat-sensitive copying material as claimed in claim 16 which comprises imidazole as a pH adjuster.

18. A heat-sensitive copying material as claimed in claim 1 having a top-coat thereon which comprises polyphenylene oxide.

19. A heat-sensitive copying material as claimed in claim 18 wherein the top-coat also comprises an ultraviolet absorbing material.

References Cited UNITED STATES PATENTS 3,3 67,797 2/ 1968 Sorensen 11736.8 3,135,607 6/1964 Hills 117-36.8 3,453,112 7/1969 Schaeffer et al 117-36.8 2,967,784 1/1961 Newman et al. 117-36.8 2,995,465 8/1961 Richey 117--36.8 3,224,878 12/1965 Klimkowski et al. 1l7--36.8 3,097,297 7/ 1963 Sahler 117--36.8 3,480,433 11/1969 Haist 11736.8

MURRAY KATZ, Primary Examiner US. Cl. X.R.

stem: Noe

nventofls) UNl'l-LU DLALLD IALLHL ri-lulu CERTIFICATE OF CORRECTION Dated September 26, 1972 Robert C. Desjarlais It is certified that error appears in the above-identified patent aid, that said Letters Patent are hereby corrected as shown below:

Column Column Column Column Column Column Column Column Column Column Column Column 7 Column Column Column Column EAL) tt'est:

" Y-1 1M. I. FLETCHER,JR'.

:,,.'-;i';ing Officer 4, line 35, after the formula, add --and the like-w- 5', line 49, extending down from "C"' should be O--'.

" 1; should be 5.6 and 9.72" should be ll, l2,

line

line

line line line line line line

line line line .line

line line line line line line line line line line

line line line 37,- under the "N" in the formula should be -H-.

22, "8.18" shouldbe -8 .l9"-and- "4.1" should 64, "7.7'.' should be '--7.75--.

31, a, 4" should be X 51, remove the lower Cl.

48, extending down from "N" should be -H 61, "(I)" should be -9. 5, after "N" insert -H.

37,, "HO" should be -0H".- o

52, "Q" should be -6.

7, "2,2-dihydroxy" should be --2,'2.' dihydroxy-m- 2, remove "found" second occurrence.

5,- after "CG" insert quotation marks 41, "hycroxy" should be -hydroxy'--.

57, "nitrosoniumion" should be --ni'trosonium .ion--. 9, l0 9" should be -l0.9--.

14, "84-95" should be -8485- 16, '92 96" should be -9296.. 7

5l "comproses" should be -comprises-. J

Signed and sealed this 8th b oi Jenu'er 1974.

RENE D. TEGTMEYER I vActing Commissioner-of Patents 

